Micro-resolution ultrasound system for aerospace composite materials using IR and HeNe lasers

Micro-resolution ultrasound is a process that can characterize materials using a focused beam immersion ultrasonic probe, an infrared (IR) laser vibrometer, an immersion tank, and a sample holder. The focused beam immersion ultrasonic probe has a spot size of 0.3mm with 20MHz at a focal point of 28mm. The focal diameter of the IR laser can be as small as 10µ, allowing for a higher probability-of-detection (POD) for defects in materials. A 3cm-by-3cm sample of molded fiber glass, similar to what is used in civil aviation aircraft was examined using both IR and HeNe lasers. A system interface using Python and MATLAB was used to automate a nondestructive evaluation process that produced microscopic resolution of the control sample (a grade-91 steel plate) and two samples of composite pieces from a Cirrus Aircraft. In conclusion, this study showed that microscopic resolution can be achieved with less sample preparation using an IR laser, in place of a HeNe laser that is traditionally used.